IL-2, IL-7 and IL-15 as immuno-modulators during SIV/HIV vaccination and treatment.

While highly active antiretroviral therapy (HAART) regimens have proven to be effective in controlling active HIV replication, complete recovery of CD4+ T cells does not always occur, even among patients with high level virologic control. Recent advances in understanding the biology of T cell production and homeostasis have created the potential to augment anti-viral therapies with immunotherapies designed to facilitate recovery of the HIV-damaged immune system, in particular, the recovery of CD4+ T cell populations. The common gamma-chain cytokines IL-2, IL-7 and IL-15 are primary regulators of T cell homeostasis and thus have been considered prime candidate immunotherapeutics, both for increasing T cell levels/function and for augmenting vaccine-elicited viral-specific T cell responses. Recent studies have established that these cytokines have distinct functional roles in immune homeostasis, which focus on specific T cell populations. The ability of these cytokines to provide immunotherapeutic benefit to HIV+ patients will depend on their ability to stably increase or functionally enhance the desired T cell target population without adverse virologic or clinical consequences.